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K⁺ absorption by locust gut and inhibition of ileal K⁺ and water transport by FGLamide allatostatins.

Authors
  • Robertson, Lisa1
  • Donini, Andrew1
  • Lange, Angela B2
  • 1 Department of Biology, York University, Toronto, ON, Canada, M3J 1P3. , (Canada)
  • 2 Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada, L5L 1C6 [email protected] , (Canada)
Type
Published Article
Journal
Journal of Experimental Biology
Publisher
The Company of Biologists
Publication Date
Sep 15, 2014
Volume
217
Issue
Pt 18
Pages
3377–3385
Identifiers
DOI: 10.1242/jeb.101774
PMID: 25013112
Source
Medline
Keywords
License
Unknown

Abstract

The scanning ion-selective electrode technique (SIET) was utilized for the first time in Locusta migratoria to characterize K(+) transport along the digestive tract and to determine the effect of two locust FGLamide allatostatins (FGLa/ASTs) on K(+) transport: a previously sequenced FGLa/AST from Schistocerca gregaria (Scg-AST-6; ARPYSFGL-NH2) and a newly sequenced FGLa/AST from L. migratoria (Locmi-FGLa/AST-2; LPVYNFGL-NH2). Regional differences in K(+) fluxes along the gut were evident, where K(+) efflux in vitro (or absorption into the hemolymph in vivo) was greatest at the anterior ileum, and lowest at the colon. Ileal K(+) efflux was inhibited by both Scg-AST-6 and Locmi-FGLa/AST-2, with maximal inhibition at 10(-10) and 10(-11) mol l(-1), respectively. Both FGLa/ASTs also inhibited cAMP-stimulated K(+) efflux from the ileum. Locmi-FGLa/AST-2 also inhibited efflux of water across the ileum. Locusts are terrestrial insects living in dry climates, risking desiccation and making water conservation a necessity. The results suggest that FGLa/ASTs may be acting as diuretics by increasing K(+) excretion and therefore increasing water excretion. Thus it is likely that FGLa/ASTs are involved in the control of hemolymph water and ion levels during feeding and digestion, to help the locust deal with the excess K(+) load (and subsequently fluid) when the meal is processed.

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